Development of crescentic bars for a periodically perturbed initial bathymetry
Development of crescentic bars for a periodically perturbed initial bathymetry
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用于周期性扰动初始测深的新月形条的开发
DOI：
10.1029/2011jf002069
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发表时间：
2011
影响因子：
--
通讯作者：
R. Garnier
中科院分区：
文献类型：
--
作者：
M. Tiessen;N. Dodd;R. Garnier
[1]使用完全非线性模型（Morfo55），将从“未受干扰”的海滩（即仅受干扰以模拟背景噪声并由此启动形态发育的海滩）开始的新月形床型的发展与从单色（在某些情况下是双色）床型预先存在的海滩开始的发展进行比较。研究了大范围的不同长度尺度和振幅。研究结果表明，新月形床型的前期存在会显著影响该海滩随后的形态发育，但这种发育与未受干扰的海滩发育有关。预先存在的床型是否在某些强迫条件下保持不变取决于预先存在的长度尺度沿着未受干扰的线性增长率曲线的位置：如果预先存在的模式在未受干扰的情况下显示出显著的线性增长，则该预先存在的长度尺度仍然存在。否则，先前存在的模式将被长度更接近未受干扰的最快增长模式的床型所取代。先前存在的明显长于未受干扰的最快增长模态的长度尺度将被原始长度尺度的更高谐波所取代；对于较短的预先存在的长度尺度，这将是线性最快增长模式。原有床型振幅的增加加速了向新的稳定状态的发展。对于较小的初始振幅，系统对预先存在的床型的初始响应理论上可以只用线性化方程来描述。已有模态和新出现模态的迁移速率与未受干扰情景下这些模态的迁移速率相对应。
[1] The development of crescentic bed patterns starting from an ‘undisturbed’ beach (i.e. one only perturbed so as to simulate background noise and thereby initiate morphological development) is compared with that starting from a beach where monochromatic (and in some cases bichromatic) bed patterns pre-exist, using a fully non-linear model (Morfo55). A wide range of different lengthscales and amplitudes is investigated. The findings suggest that the pre-existence of crescentic bed-forms can influence the subsequent morphological development of this beach significantly, but that this development is related to the undisturbed beach development. Whether a pre-existing bed-form remains under certain forcing conditions depends on the position of the pre-existing lengthscale along the undisturbed linear growth rate curve: If the pre-existing mode shows significant linear growth in the undisturbed scenario, this pre-existing lengthscale remains. Otherwise the pre-existing mode will be replaced by a bed-form with a lengthscale closer to the undisturbed fastest growing mode. A pre-existing lengthscale that is significantly longer than the undisturbed fastest growing mode will be replaced by a higher harmonic of the original lengthscale; for shorter pre-existing lengthscales, this will be the linear fastest growing mode. An increased amplitude of the pre-existing bed-form accelerates the development toward a new stable situation. For small initial amplitudes, the initial response of the system to pre-existing bed-forms could theoretically be described using linearized equations alone. The migration rates of both the pre-existing and newly arising modes correspond to the migration rate of these modes in the undisturbed scenario.